[IPOL announce] new article: Local JPEG Grid Detector via Blocking Artifacts, a Forgery Detection Tool

[announcements about the IPOL journal]

A new article is available in IPOL: http://www.ipol.im/pub/art/2020/283/

Tina Nikoukhah, Miguel Colom, Jean-Michel Morel, and Rafael Grompone von 
Gioi,
Local JPEG Grid Detector via Blocking Artifacts, a Forgery Detection Tool,
Image Processing On Line, 10 (2020), pp. 24–42.
https://doi.org/10.5201/ipol.2020.283

Abstract
Image JPEG compression leaves blocking artifact traces. This paper 
describes an algorithm that exploits those traces to locally recover the 
grid embedded in the image by the JPEG compression. The algorithm 
returns a list of grids associated with different parts of the image. 
The method uses Chen and Hsu's cross-difference to reveal the artifacts. 
Then, an a contrario validation step according to Desolneux, Moisan and 
Morel's theory delivers for each detected grid a Number of False Alarms 
(NFA) which tells how unlikely it is that the detection is due to 
chance. The only parameter is the step size of the windows used, which 
represents the exhaustiveness of the method. The application to image 
forgery detection is twofold: first, the presence of discrepant JPEG 
grids with low NFA is a strong forgery cue; second, knowledge of the 
grid is anyway required for further JPEG forensic analysis.